1. Field of the Invention
This invention relates generally to audio acoustic echo cancellation in audio and video conferences.
2. Description of the Related Art
One issue in an audio or video conference, where the participants use an open microphone and speakers, is acoustic echo cancellation. We use speakers to mean any sort of audio output device, and microphones to mean any sort of audio capture device. Acoustic echo is created as follows. A speaker A's voice is played back from another participant B's speaker. B's microphone captures B's speech. However, it may also capture the playback of A's voice. The audio stream from B is sent to A, who then hears the echo of his voice.
Software echo cancellation techniques have been tried in the past for real-time audio-conferencing systems. However, none of these seem to work well without compromising some quality. The software-based techniques usually require that the sampling frequencies throughout the conferencing system are accurate and the same, and often also require there is no packet loss over a network. In reality, even in the zero-packet loss situation, with the same sampling frequencies specified on the capture and playback side, the cancellation techniques do not seem to work well. One reason is because, even though the same sampling frequency is specified through the system, the actual sampling frequency will vary due to hardware and operating system issues. That is, the different components in the conferencing system do not use exactly the same sampling frequencies, thus violating a basic assumption of many echo cancellation techniques.
Thus, there is a need for better audio acoustic echo cancellation techniques.
The figures depict embodiments of the present invention for purposes of illustration only. One skilled in the art will readily recognize from the following discussion that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the invention described herein.